The function of machine tools is in general to generate component geometries of a workpiece, preferably with machining techniques, which component geometries are precisely defined in terms of shape, position and dimensions. In this context, the requirements with regard to accuracy are becoming ever greater, wherein not only a hundredth, but also, at least in part, even a thousandth of a millimeter accuracy is demanded.
A rotary table is a part of a machine tool, on which workpieces are clamped for machining. The rotary table has a vertical or, in some applications, a horizontal rotational axis, about which a rotary plate or indexing plate, or workpiece table, can be rotated with the clamped workpiece, so that metal cutting operations can be performed in various positions or on the rotating workpiece. Thus, the rotary tables can be used for turning or milling.
Depending on the application, servomotors with gearing, or often also direct drives with torque motors, are employed as the drives.
In metal cutting, in recent decades the requirements regarding accuracy and rigidity, as well as the maximum possible rotation speed of the rotary table, have become ever greater. Thus, depending on the application, the rotary tables have hitherto been designed, with regard to turning, with relatively high rotation speeds, generally greater than 1000 revolutions per minute or, on the other hand, with regard to milling, with high rigidity.
Also higher rotation speeds result in a stronger heat load upon the respective components, and thus to greater thermal stresses, which generates adverse deformations/changes with respect to the achievable accuracy in the machining. This reduces the suitability of the rotary table for turning.